Recently, there is a growing demand for images with high resolution and high quality such as high definition (HD) images and ultra high definition (UHD) images in various fields. In comparison with the existing image data, high resolution and high quality image data requires a relatively great information amount or bit amount. Therefore, a transmission cost and a storage cost are increased when the image data is transmitted by using a medium such as the existing wired/wireless broadband line or when the image data is stored by using the existing storage medium. To solve these problems, high-efficient image compression techniques may be used.
As the image compression technique, there are various techniques such as an inter prediction technique which predicts a pixel value included in a current picture from a previous and/or next picture of the current picture, an intra prediction technique which predicts a pixel value included in a current picture by using pixel information in the current picture, an entropy encoding technique which allocates a short codeword to a value having a high appearance frequency and allocates a long codeword to a value having a low appearance frequency, etc. Such an image compression technique may be used to transmit or store image data by effectively compressing the image data.